In general, in order to perform smooth and efficient traffic easy-going in an intersection, a signal waiting time must be minimized. For such smooth and efficient traffic easy-going, to prevent a spillback phenomenon in an intersection which generates a traffic barrier and to minimize the green time when there is no passing vehicle and to extend the green time, if necessary, may be said to be the key.
Accordingly, a signal control method now most used in intersections is a fixed cycle signal control method in which a signal cycle (the time taken for the green lighting of a traffic light for each green time movement to rotate once) and a phase time (the time during which the green light of each traffic light is turned on) are fixed.
However, such a fixed cycle signal control method has a problem in that an accidental change in the volume of traffic attributable to a frequently changing traffic condition, such as a spillback phenomenon suddenly generated due to a traffic accident or a sudden reduction in the volume of traffic, cannot be handled.
In order to solve such a problem, conventionally, a signal control method according to an actual volume of traffic in real time other than signal control using the fixed cycle signal control method is adopted. However, in performing the signal control method according to the volume of traffic, in order to detect the volume of traffic, a detection area using detection means, such as a loop sensor or a camera, is set in a street (a carriageway along which vehicles can pass) ahead of an intersection, but the detection area is set to detect the volume of traffic in each carriageway. In this case, however, there is a problem in that a cost for installation and maintenance and repair is high because the detection area increases in proportion to the number of carriageways. If one carriageway is a shared carriageway also used for going-straight, right-turn and going-straight and left-turn, there is a limit to the improvement of a signal operation or efficient signal control because vehicle pass information cannot be classified and detected for each green time movement.
Furthermore, an already developed intersection spillback phenomenon prevention technology included a method of setting a detection area by disposing detection means in a specific street section of a carriageway, calculating a vehicle speed based on detected information (data), determining a spillback phenomenon based on specific speed criteria, and then changing a green signal to a red signal.
However, the above method is a method of simply changing information about the street occupation time of a vehicle into speed information. Accordingly, there is a good possibility that an error occurs, such as when speed is reduced due to a simple obstacle or stop ahead of an intersection, other than a spillback phenomenon within the intersection because the method is not based on an actual vehicle speed within the intersection.
Furthermore, in the already developed method, in order to prevent a spillback phenomenon, a next phase is performed right after a red signal. Accordingly, there was a problem in that efficiency is very low, such as that the passing of a vehicle in a different green time movement in the state in which an intersection blockage phenomenon is present is performed or one phase switches to a next phase although a spillback phenomenon has been rapidly solved.
Furthermore, conventional intersection signal control methods include a method of sending vehicle detection information collected in a detection area in a street section to a traffic control center in a remote place and determining, by a constructed program or an expert in the traffic control center, a signal operation based on the vehicle detection information. The method had problems in that rapidness (processing time) and efficiency are low because a traffic signal is controlled in a remote place and a cost for operations and maintenance and repair is high.